1. Field of the Invention
The present invention relates to a plasma processing apparatus, which generates plasma in a chamber maintained in a vacuum state and processes a substrate using the plasma.
2. Description of the Related Art
Plasma processing apparatuses, which process the surface of a substrate using plasma, have been widely used in a process for manufacturing a semiconductor device and a liquid crystal display device. The plasma processing apparatuses include a plasma etching apparatus for performing etching of a substrate and a plasma Chemical Vapor Deposition (CVD) apparatus for performing CVD of a substrate.
As shown in FIG. 1, a plasma processing apparatus 1 comprises two flat plate-type electrodes 10 and 20 located in parallel such that they face each other. A substrate S is mounted on the lower electrode 20. Accordingly, the lower electrode 20 may be referred to as “a substrate mount”.
Further, internal elevating pins 30 and external elevating bars (not shown) for assisting the carrying of the substrate S into and out of the plasma processing apparatus 1 are provided in the plasma processing apparatus 1, as shown in FIG. 1. The internal elevating pins 30 are located in through holes 22 formed through edges of the lower electrode 20, and move vertically in the through holes 22.
The external elevating bars are provided at the outside of the lower electrode 20. That is, the external elevating bars are located in spaces formed between side walls of the lower electrodes 20 and the side walls of the plasma processing apparatus 1, and move vertically.
An exhaust unit 40 for exhausting inner gas to the outside is formed through the plasma processing apparatus 1. The exhaust unit 40 removes gas in the plasma processing apparatus 1 by suction and maintains a vacuum state of the plasma processing apparatus 1 using a pump (not shown) provided at the outside of the plasma processing apparatus 1.
The upper electrode 10 is located at a position facing the lower electrode 20. The upper electrode 10 serves as a process gas supply unit for supplying process gas to a space between the upper and lower electrodes 10 and 20 as well as an electrode. Accordingly, as shown in FIG. 1, a shower head 12 is connected to the lower portion of the upper electrode 10. The shower head 12 has a plurality of process gas diffusing holes 14 having a fine diameter. The shower head 12 uniformly supplies the process gas to the space between the upper and lower electrodes 10 and 20. The process gas supplied to the space between the upper and lower electrodes 10 and 20 is converted into plasma by high-frequency power applied to the upper and lower electrodes 10 and 20, and the plasma processes the surface of the substrate S.
A refrigerant channel 16 for circulating a refrigerant therethrough is formed in the upper electrode 10. The refrigerant channel 16 passes through the upper electrode 10 in the horizontal direction, and is uniformly disposed throughout all regions of the upper electrode 10. One end of the refrigerant channel 16 is connected to a refrigerant supply pipe 17 communicating with the outside, and the other end of the refrigerant channel 16 is connected to a refrigerant collection pipe 18. Accordingly, the refrigerant channel 16 receives a new refrigerant from the refrigerant supply pipe 17 and returns the waste refrigerant to the refrigerant collection pipe 18, thereby circulating the refrigerant. The refrigerant channel 16 serves to prevent a process performed by the plasma processing apparatus 1 from being affected by the increase in the temperature of the shower head 12 due to the generation of plasma.
Since the conventional plasma processing apparatus 1 has the refrigerant channel 16, which is not formed directly in the shower head 12 but is formed in the upper electrode 10, so that the shower head 12 is indirectly cooled, it is not easy to control the temperature of the shower head 12. When the temperature of the shower head 12 is increased due to the difficulty in controlling the temperature of the shower head 12, high-frequency power transmission efficiency is decreased and affects etch rate or uniformity in etching, thereby deteriorating the reproducibility of plasma treatment.